Cryptic Disseminated Tuberculosis: a Secondary Analysis of Previous Hospital-Based Study

Background: The main purpose of this study was to describe the demographic and clinical features of cryptic disseminated TB; it was also aimed to shed light on diagnostic test, procedure results, organ involvement, and outcomes of cryptic disseminated TB in patients with confirmed disseminated TB. Materials and Methods: We performed a secondary post hoc analysis of collected data from our previous study entitled “Disseminated Tuberculosis among Adult Patients Admitted to Hamad General Hospital, Qatar: A Five-Year Hospital-Based Study” with modified objectives. This study included patients admitted from January 1, 2006 to December 31, 2010. Results: Twenty-three patients were recruited with non-miliary patterns on chest x-ray. Their mean age was 34.4±12.6 years and 15 (65.6%) were males. The mean duration of illness was 46.13±48.4 days and the most common presenting symptom was fever in 20 patients (87%), while 3 (13%) patients had underlying medical conditions with diabetes mellitus 2 (8.7%), being the most common. Bronchoalveolar lavage (BAL) and bronchial wash (BW) fluids were Acid-fast bacilli (AFB) positive in 1/4 (25%) of the cases and culture-positive for Mycobacterium tuberculosis (M. tuberculosis) in 4/4 (100%) of all the cases. Two patients (8.7%) had positive sputum smear, while 18 (78.3%) patients had positive culture for M. tuberculosis. All except one patient completed their treatment in Qatar. One patient died one month after the start of antituberculous treatment. Conclusion: Cryptic disseminated TB should be suspected when a patient from TB-endemic countries develops unexplained fever and cough despite normal or non-miliary pattern chest radiograph. Moreover, respiratory specimen cultures should be obtained from these patients, regardless of the symptoms presented and the initial site of the involved organ.


INTRODUCTION
Disseminated tuberculosis (TB) is defined as mycobacterial disease that has two or more non- The term cryptic disseminated TB describes patients who have disseminated TB with less "typical" chest radiographic abnormalities, including normal and nonmiliary pattern (3)(4)(5)(6). It has an insidious form of presentation that mainly affects the middle-aged and elderly (3,4). Diagnosing disseminated TB in such patients TANAFFOS is still a dilemma, from both a clinical and laboratory perspective because of the lack of localizing signs, absence of choroidal tubercles, normal chest x-rays, and negative tuberculin skin test. Currently available data on this clinical entity worldwide are sparse and of limited quality (3)(4)(5)(6); this prompted us to perform this post hoc analysis.
The purpose of this study was to describe the demographic and clinical features, diagnostic tests, procedural results, and outcomes of cryptic TB in patients with disseminated TB.

Design and Setting
We performed a secondary post hoc analysis of collected data from our previous study entitled

Ethical Consideration
Since this was a secondary post hoc analysis of collected data from our previous study, no ethics committee approval or informed consent was required.
The original study was approved by Medical Research Ethical Committee at Hamad Medical Corporation, Qatar (approval no. 12080/12).

Data Analysis
The SPSS software (v 17.0; IBM Corp, Armonk, NY, USA) was used for data analysis and post-analysis results of continuous variables were expressed as means and standard deviations (SD). No patient had a prior history of tuberculosis.

Of
Tuberculin skin tests were positive in 43.5% (10/23) of the cases and erythrocyte sedimentation rate ranged between 2 and 137 mm/h (mean 49.42±30.60). Table 2 summarizes the main hematological findings in our patients.
Therefore, respiratory specimens should be obtained for AFB, PCR, and mycobacterial culture from all patients with suspected disseminated TB, regardless of the symptoms presented and the initial site involved.
As noted in this study, the mortality was 4.3% which is less than the range of 46-80% reported in the literature (6,8).
There were limitations to this study. First, it was retrospective with a small sample size. Second, it was hospital-based. Third, PCR study on different specimens, especially respiratory, was not used because it was not available in our laboratory during the study period.
Despite this, we believe that this study is the first step in exploring the details of this clinical entity in Qatar.
Therefore, we recommend conducting large prospective studies to confirm our findings.
In conclusion, cryptic disseminated TB is a recognised clinical entity which poses a significant diagnostic challenge for clinicians. It should be suspected when a patient from TB-endemic countries has unexplained fever and cough despite a normal or non-miliary pattern chest radiography. Moreover, respiratory specimen cultures should be obtained from these patients, regardless of the symptoms presented and the initial site of the involved organ.

Conflict of Interests
There are no conflicts of interest to declare.

Ethical Considerations
There was no need for an ethical approval, as it was a secondary post hoc analysis of collected data from our previous study

Financial Disclosure
There is no financial disclosure.

Funding/Support
The current study received no financial support.